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Density of NMDA‐Coupled and Uncoupled 1‐[1‐(2‐[ 3 H]Thienyl)cyclohexyl]piperidine Recognition Sites in the Brain and Spinal Cord: Differential Effects of NMDA Agonists and Antagonists
Author(s) -
Kovács Katalin J.,
Larson Alice A.
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.63051757.x
Subject(s) - nmda receptor , spinal cord , chemistry , binding site , central nervous system , population , receptor , biophysics , anesthesia , neuroscience , biology , biochemistry , medicine , environmental health
Binding of 1‐[1‐(2‐[ 3 H]thienyl)cyclohexyl]piperidine ([ 3 H]TCP) to mouse brain and spinal cord membranes was studied using compounds selective for the NMDA‐coupled 1‐(1‐phenylcyclohexyl)piperidine (PCP) and/or σ recognition sites. In both tissues, [ 3 H]TCP labeled two populations of binding sites. Density of the low‐affinity sites was approximately the same in both tissues, but the population of the high‐affinity [ 3 H]TCP sites was three times bigger in the brain than in the spinal cord. Self‐ and cross‐displacement studies showed that the high‐affinity [ 3 H]TCP binding sites could be identical with NMDA receptor‐coupled PCP sites, whereas the low‐affinity [ 3 H]TCP sites may be associated with σ binding sites in both tissues. The NMDA‐coupled PCP sites labeled in the presence of 6.25 n M [ 3 H]TCP constituted a much higher percentage of the total binding in the brain (75%) than in the spinal cord (44%). Consistent with this, reintroduction of glycine and glutamate significantly increased, but DA antagonists significantly inhibited [ 3 H]TCP binding in the brain but not in the spinal cord. Together, these data suggest that a large component of [ 3 H]TCP‐labeled binding sites in the spinal cord may be associated with σ but not the NMDA receptor‐coupled PCP sites.